package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.extra.ssh.JschUtil;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.RedisConstants;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.concurrent.TimeUnit;

/**
 * <p>
 *  服务实现类
 * </p>
 *
 * @author 虎哥
 * @since 2021-12-22
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {

    @Autowired
    private StringRedisTemplate stringRedisTemplate;

    @Override
    public Result queryById(Long id) {
        //缓存穿透
        //Shop shop = queryWithPassThrough(id);

        //互斥锁解决缓存击穿
        Shop shop = queryWithMutex(id);

        if (shop == null) {
            return Result.fail("店铺不存在!");
        }
        //7.返回
        return Result.ok(shop);
    }

    public Shop queryWithMutex(Long id){
        String key = RedisConstants.CACHE_SHOP_KEY+id;
        //1.从redis中查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(RedisConstants.CACHE_SHOP_KEY+id);
        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在直接返回
            return JSONUtil.toBean(shopJson,Shop.class);
        }
        // 判断命中的是否是空值
        if(shopJson!=null){
            return null;
        }

        //开始实现缓存重建，
        //1）获取互斥锁
        String lockKey = "lock:shop:" + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //2）判断是否获取成功
            if(!isLock){
                //3）失败，休眠并重试
                Thread.sleep(50);
                queryWithMutex(id);
            }

            //4）成功，根据id查询数据库
            //4.不存在
            shop = getById(id);
            //5.数据库中也不存在
            if(shop == null){
                //将空值放入redis
                stringRedisTemplate.opsForValue().set(key,"",RedisConstants.CACHE_NULL_TTL,TimeUnit.MINUTES);
                return null;
            }
            //6.存在也存入redis
            stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }finally {
            //释放互斥锁
            unLock(lockKey);
        }
        //7.返回
        return shop;
    }

    /**
     * 获取锁
     * @param key
     * @return
     */
    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    /**
     * 释放锁
     * @param key
     */
    private void unLock(String key){
        stringRedisTemplate.delete(key);
    }

    @Override
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if(id ==null){
            return Result.fail("店铺id不能为空");
        }
        //1.更新数据库
        updateById(shop);
        //2.更新缓存：直接对缓存进行删除
        stringRedisTemplate.delete(RedisConstants.CACHE_SHOP_KEY+shop.getId());
        return Result.ok();
    }

    /**
     * 缓存穿透解决方案
     * @param id
     * @return
     */
    public Shop queryWithPassThrough(Long id){
        String key = RedisConstants.CACHE_SHOP_KEY+id;
        //1.从redis中查询缓存
        String shopJson = stringRedisTemplate.opsForValue().get(RedisConstants.CACHE_SHOP_KEY+id);
        //2.判断是否存在
        if(StrUtil.isNotBlank(shopJson)){
            //3.存在直接返回
            return JSONUtil.toBean(shopJson,Shop.class);
        }
        // 判断命中的是否是空值
        if(shopJson!=null){
            return null;
        }
        //4.不存在
        Shop shop = getById(id);
        //5.数据库中也不存在
        if(shop == null){
            //将空值放入redis
            stringRedisTemplate.opsForValue().set(key,"",RedisConstants.CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }
        //6.存在也存入redis
        stringRedisTemplate.opsForValue().set(key,JSONUtil.toJsonStr(shop),RedisConstants.CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //7.返回
        return shop;
    }
}
